The reserve consisted of the 6th Carabineers; four troops of the 9th Light Dragoons, all dismounted; a part of the 88th regiment; pickets from all these regiments, which remained in charge of the knapsacks and great-coats of the men; about forty of the 17th Light Dragoons, mounted, and such of the artillery as had not been left with Colonel Mahon at Quilmes.
General Crauford had two light field-pieces attached to his column, the other columns were without artillery.
Colonel Duff of the 88th regiment had such misgivings as to the result of the day that he left the colours of his regiment behind him with the reserve, and, when he advanced before dawn to the head of the street by which he was to enter the city, he found his regiment so weak that he sent back for two of the companies which had been left with the reserve. Before these companies were allowed to join him they were ordered to take the flints from their muskets and leave them behind, and Colonel Duff lost much time in trying to provide them with flints, by searching among the rest of his men for spare ones. Even so, many of the men of these two companies entered into action without flints.
The division under the command of Colonel Mahon, which advanced from Quilmes to the Puente Galvès on the 5th July, consisted of about 1800 men, infantry, artillery and dismounted cavalry, the 9th and 17th Light Dragoons, and 200 sailors from the squadron, who had been landed by Admiral Murray to assist in dragging the cannon through the swamps at Ensenada, where five guns captured from the Spaniards at Monte Video stuck fast and were destroyed by Colonel Frazer.
The idea of General Whitelock appears to have been, that by avoiding the main streets of the city, which led direct from the Corrales to the Plaza Mayor, and by a rapid march before sunrise, without firing, through the suburbs and shorter streets, he would succeed in surprising the principal positions to the north and south of the great square, which idea, considering that most of these positions were a league distant from the Plaza Miserere, presumed a great want of vigilance on the part of the garrison, while all chance of a surprise was effectually destroyed by the way in which the signal to advance was given.